1. Field of the Invention
The present invention relates to a semiconductor nitride film etching system for stabilizing a nitride film etching rate of a semiconductor wafer and an etching selection ratio.
2. Discussion of the Background
Semiconductor nitride films with various properties can be formed by various methods at present, and therefore various applications in semiconductor manufacturing are increased. As the integration level of a semiconductor device rises, the structure of the device is further complicated, and types of coexistent films depend on the process to which the films are applied.
In general, nitride film etching has used wet treatment and a treatment solution containing hot phosphoric acid so far. However, as the integration level of a device rises and the structure of the device is further complicated, nitride films and oxide nitride films with various properties are used. Therefore, it is difficult to etch these films of the nitride-film system by the conventional hot phosphoric acid treatment with high controllability. [0003]
In a semiconductor manufacturing process, because the sectional form and the cleanliness of an integrated circuit after etching are important, it is very important to control the etching selection ratio between a nitride film to be etched and other coexistent films (e.g. SiOxNy-based film: 0.ltoreq.x, y.ltoreq.2). The etching selection ratio is determined by an equilibrium reaction relating to etching, and hence, an etchant, reaction product, and temperature serve as parameters of the reaction rate of the equilibrium reaction. Therefore, to realize accurate etching, it is indispensable to control these parameters.
FIG. 21 shows a configuration of a conventional circulation-type nitride film etching system. The conventional etching system is constituted so as to circulate the treatment solution through a treatment tank 1, while passing the solution through a filter 3 by a pump 2, and heating the solution by a heater 4, and supplying demineralized water by a demineralized-water dripping apparatus 5. This type of etching system is constituted so as to control the concentration and temperature of only phosphoric acid in the treatment solution, but it cannot control other components in the treatment solution.
Therefore, it is difficult to optionally and stably obtain the etching rates of a nitride film and other films, and the selection ratio between the nitride film and other films.
The present invention is made to solve the above problems and its object is to provide a semiconductor nitride film etching system for improving treatment solution performance and stabilizing the etching rate of a semiconductor nitride film and the etching selection ratio.